1. Field of the Invention
The present invention relates to automotive vehicles, more particularly to, fluid flow through a throttle body on an engine for automotive vehicles.
2. Description of Related Art
Currently, a throttle body on an engine has a throttle plate for controlling the amount of air that flows to the cylinders of the engine. During engine operation, the amount of air desired to perform idle speed conditions is typically controlled electronically. The path for the air to travel starts above the throttle plate, bypassing the throttle plate via a drilling from inside the throttle body, to an orifice that meters the air by means of an electronically controlled stepper motor. The air metered from the orifice is finally dumped below the throttle plate to be mixed with fuel downstream.
One problem with the current system is that a failure of the stepper motor may cause the engine to surge if a high amount of bypass air flows past the throttle plate during engine idle. Also, the engine may stall if not enough bypass air is allowed to flow during engine idle.
To overcome these problems, a solenoid-actuated valve is used to divert a predetermined amount of fluid flow to bypass the throttle plate. An example of this is disclosed in a copending application entitled "Idle Bypass System" in the name of Daryl Codling, which is hereby incorporated by reference. Although this system works well, a large size solenoid has to be used to deliver the power necessary to move the valve.
It is, therefore, one object of the present invention to provide an idle bypass flow path that will allow a predetermined amount of air to flow past the throttle plate to the intake manifold if a failure of the stepper motor occurs. It is another object of the present invention to reduce the size and power of the solenoid to move the valve from one position to another.
SUMMARY OF THE INVENTION
Accordingly, the present invention is an idle fluid flow shutoff assembly for allowing a predetermined amount of fluid flow to an intake manifold of an engine. The assembly includes a throttle body having a longitudinal axis and means forming a central passageway along the axis. A throttle plate means is disposed within the central passageway transversely to the longitudinal axis for rotation between an open and closed position to allow fluid flow through the central passageway. The throttle body includes means forming a secondary passageway having an inlet communicating with the central passageway upstream of the throttle plate means and an outlet communicating with the intake manifold downstream of the throttle plate means to allow fluid flow to bypass the throttle plate means when in the closed position. A motor means is secured to the throttle body and cooperates with the secondary passageway for allowing a predetermined amount of fluid flow through the outlet. A pressure-acuated valve means is moveable in response to the absence and presence of a predetermined pressure level and cooperates with the secondary passageway to block fluid flow to the motor means and allow a predetermined amount of fluid flow to the intake manifold when the amount of fluid flow past the motor means is not within predetermined limits.